The Israeli military has carried out an air strike on the Gaza Strip, targeting what it said were Palestinian militants preparing to fire rockets into Israel.
Palestinian medical sources said four civilians were injured, one of them critically. Hamas officials said the attack had occurred near a cemetery.
But Israel said a member of a Salafist militant group, Jaljalat, was killed.
On Thursday, two Palestinians were injured in an air strike on smuggling tunnels near the border with Egypt.
The strike reportedly came in response to to rocket fire the previous day by Palestinian militants.
Incidents of rocket fire from Gaza have decreased since Israeli forces launched a large-scale offensive last December and January, but there have been sporadic attacks.
In a statement issued on Friday morning, the Israeli military said its air force had attacked a group of militants "on their way to fire rockets from the northern Gaza Strip".
"Accurate hits, including the rocket launching pad, were identified," it added.
But the Hamas movement, which controls Gaza, said civilians who had been on their way to visit the graves of relatives were hit.
According to reports from Gaza, a group called Jaish al-Umma (Army of the Nation), an Islamist militant group affiliated with al-Qaeda, has said it fired several mortars into Israel overnight.
However, the Israeli army has said it was only aware of two mortars fired on Thursday, and that they did not reach Israel.